Updated Czech translation
Merge pull request #380 from milankni/translation-cz

Updated Czech translation
mention lua in the release notes
Go through git log and update the RELEASE_NOTES
Remove 'pl' from doc/usermanual/po/LINGUAS, as there is no corresponding pl.po
Merge pull request #383 from levitte/usermanual-fixes

Remove 'pl' from doc/usermanual/po/LINGUAS,...